Principle: circular signs give orders.

Principle within that: red signs give prohibitions. Blue signs are positive instructions (e.g. keep left)

Yes - it is confusing - especially for foreigners.

Some other countries do have a red line across to indicate no motor vehicles.

Before reading highways code I also thought it is cars & motorcycles only :-)

First sign is: all motor vehicles prohibited.

Second sign is: No right turn. That could mean other vehicles, push bikes etc.

Suggest you get an up to date copy of the highway code and learn it!

Who on these posts does not know what they mean?